Up to now, as a radiator that cools the heater element, heat sinks have been generally widely used. The heat sinks are roughly classified into one heat sink in which radiation fins and a radiation fin support base are integrated together by die cast molding or extrusion molding, and another heat sink in which the radiation fins and the radiation fin support base are individualized and combined together. In the latter, by the radiation fins and the radiation fin support base being individualized, a restriction of strength of a die necessary for the extrusion molding or the die cast molding can be relaxed, and therefore, a fin pitch between the adjacent radiation fins can be narrowed or a radiation fin length can be lengthened. Accordingly, as compared with the former, the latter is effective in reducing costs attributable to a reduction in an installation area of a semiconductor device or a reduction in a size of the heater element.
Also, there is a swaging method as a method of fitting the radiation fins with the radiation fin support base in a configuration where the radiation fins and the radiation fin support base are individualized and combined together. As this method, for example, Patent Literature 1 discloses a radiator in which plural grooves are formed in parallel to a plane of the radiation fin support base in advance, side edges of the radiation fins are fixed with the grooves from above, and a tip of a swaging tool is pushed against plural different grooves each formed between the plural adjacent grooves to forcedly narrow the grooves fixed with the side edges of the radiation fins.
Also, Patent Literature 2 discloses a technique by which the grooves of the radiation fin support base are formed into a taper shape so as to expand from openings of the grooves toward bottoms thereof, and both sides of each groove bottom are rounded. Accordingly, when the radiation fins are swaged in the grooves, the radiation fins are deformed into an expanded taper shape along the groove shape, and pressed and fixed into the grooves.